Method of forming restrictors



Dec. 17, 1940. 0. M SUMMERS METHOD OF FORMING RESTRIGTORS Filed Juh'e 1, i956 9 WW 7 Z 6 m 2 a a 2 ENTOI? BY 941461 ATTORNEY Patented Dec. 1" 7, 1940 PATENT OFFICE 2 2,225,513 METHOD or FORMING nas 'rnrcroas Otto M. Summers, Dayton,

Ohio, assignor to General Motors Corporation, Dayton, Ohio, a

corporation of Delaware Application June 1, 1936, Serial No. 82,723

' 2Claims.

- This invention relates to refrigerating apparatus and more-particularly torestrictors for controlling the flow of liquid refrigerant to evaporators and the method and machine for making 5 and gauging said restrictors.

An object of the invention is to improve upon restrictors and the method and machine for making and gauging said restrictors whereby greater accuracy and uniformity may be had at a greatly in reduced cost.

In the past, efforts have been made to utilize the regular commercial copper or. other metal tubing of small diameter for restrictor purposes, but due to the lack of uniformity in the tubing,

it has been impossible to utilize the commercial tubing, and efior'ts to secure special tubing of the proper cross-section and necessary uniformity throughout have failed.

One object of this invention is to make use of this regular commercial tubing in the manufacture of restrictors having the necessary. uniformity throughout.

It is also an object of this invention to devise means whereby resistance to flow of fluid through the tubing may be increased by adding an increment of resistance throughout the entire length of the tubing.

A still further object of this invention is to provide new and improved means for gauging the resistance to the flow of fluid through the restrictor.

Further objects and advantages of the present invention will be apparent from the following description, reference being had to the accompanying drawing wherein preferred forms of the present invention are clearly shown.

In'the drawing:

Fig. 1 shows a diagrammatic view of a refrigerating device employing one form of applicants 40 restrictor;

Fig. 2 is a cross-sectional view of tubing used in the manufacture of applicant's device;

Fig. 3 is a cross-sectional view showing the same tubing with the inside area reduced and showing the roller means for reducing the area; and

Fig. 4 is a cross-sectional view of the apparatus used in the manufacture and gauging of the restric'tor.

1 Referring now to the drawing, andmore particularly to Fig. 1, there is shown a conventional compressor unit 8, condenser 9, restrictor l0 and evaporator II. The reference numeral l2 desi nates the usual vapor line leading from the evaporator to the compressor and reference numeral l3 designates the usual high side line leading from the compressor to the condenser 9. In units of this type, a very fine balance is neces sary and the length and cross-section of the restricter is critical. 5

In Fig. 2 is shown a section of commercial copper or other metal tubing ll which has a cross-sectional area of greater diameter than required for restriction purposes.

Fig. 3 shows the same tubing after having been 10 deformed by passing between a plurality of rollers i8 which are old and well known in mechanical arts and need no further description.

In this invention, tubing of any desired economical size and shape may be used. The cross- 15 section of the tubing is uniformly reduced throughout the length of the tubing to any desired limit in the manner disclosed in Fig. 3, so as to increase the restriction. Applicant has devised the precisionmechanism shown in Fig. 4 20 whereby the tube after having been deformed as described above, may be twisted or stretched to further'increase the restriction by very small increments. A The mechanism comprises two arms [8 and i9 mounted on a support [1, one of 5 which rotatively supports a hollow member 20 which can be rotated by means of worm wheel 2| attached thereto in any convenient manner. The worm wheel 2| may be rotated by means of warm 22, which worm may be either manually 30 rotated or mechanically rotated. The tubing to be used is supported between the arm [8 and the rotatable member-20 as shown in the drawing. The left end of the tubing is held from rotation by the-arm 18, whereas the right end of 5 the tubing is secured to the rotatable member 20 by means of a chuck 23. The left'end of the tubing is connected .to the source of fluid maintained at a constant predetermined pressure.

It has been found that by twisting the 'de- 40 formed tubing M, the restriction to the flow of fluid therethrough is increased throughout the length of the tubing subjected to the twisting operation. In order to determine the proper amount of twisting necessary, the vertical mem-- '45 ber 29 provided with gauge marks 30 is mounted a short distance away from the outlet of the rotatable member 20 so that as the tubing is twisting it is possible to determine the point where no further twisting is necessary by ob- 50 serving the height at which the jet 3| passes the gauged member 28. Sometimes it may be considered expedient to twist the tube without stretching the tube, in which case the thumb nut 32 is loosened so that in place of stretching the tubing, the arm I may move closer tothe arm It. The spring member 33 has just enough resiliency to hold the tubing taut, but not resiliency enough to cause the tubing to stretch. In the event that one would want to stretch the tubing without twisting the tubing, all that would be necessary would-be to loosen the thumb nut 32 and tighten the thumb screw Ill until it would bear against the arm l8 and force it away from .the arm IS. The preferred manner of increasing the restriction of the tubing, however, is to keep the thumb nut 32 tightened at all times so that by simply rotating the member 2| the tubing will be twisted and stretched. The means for supplying fluid at a constant predetermined pressure generally designated by the numeral II is all conventional structure. The fluid under pressure passes through the constantpressure valve 21 into the valve 26 through thegauge 25 and the constant flow restrictor 24 in the usual manner,

The tubing used is purchased in long lengths andv passed through the reducing rollers, as shown in Fig. 3, before cutting into the desired lengths. In the next step, the ends of the tubing are closed and the tubing is fully annealed.

A hydrogen atmosphere may be provided for theannealing operation, inwhich case the ends need not be closed. The tubing. is then cut into the proper lengths, fitting I5 is attached and the tubing is inserted in the precision mechanism as shown in Fig. 4 where it is further deformed.

An advantage of my method of manufacturing av restrictor is that commercial tubing of nonuniform cross-sectional.area may be inserted in my novel machine in such a manner that fluid may be supplied to the tubing at one end and discharged through the tubing at the other end during the deformationperiod.

Another advantage of the device shown in Fig. 4 is that by applying a localized force to the one end of the tubing an increment of resistance is added through the entire length of the tube.

The restrictors manufactured in accordance with applicant's invention, have a proportionately large inside surface area in comparison to the cross-section of the tube. Theshape of the opening, which is substantially triangular without any sharp corners, together with the large inside surfaoe'area combine to oifer resistance to the flow of liquid through the tubing.

While the form of embodiment of the present invention as herein disclosed constitutes a preferred form, it.is to be understood that other forms might be adopted, all coming within the scope of the claims which follow.

the length of a tube and rotating one clamped portion relative to the other clamped portion to uniformly twist and restrict the entire length of tubing between the clamped portions, simultaneously gauging the flow of fluid therethrough and discontinuing relative rotation when the gauging indicated proper'restriction to the flow 35 of fluid therethrough.

OTTO .M. SUMMERS. 

